The long-term goal of this research is to correlate the fine structure and histochemical characteristics of the peripheral sensory and autonomic end organs with their functions under normal, experimental and pathological conditions. The work is carried out in man and other mammals using electron microscopical and histochemical techniques in combination with neurohistological surveys. The material comprises skin, mucous membranes and selected autonomic supply areas of normal, pathological and experimental cases. In man, the investigation also covers individual and age variations, including fetal development of the nerve endings, and their involution during later life. In order to relate the sensory end organs with their probable functions, particular attention is being directed to their microtopographical distribution and to the relationship of their neural components to the associated non-nervous tissue elements.